Contents

Summary

Did you know?

Southern dodder was not known in New York until 1996 when it was discovered in a red maple-sweetgum swamp on Staten Island. The common name may come from a Middle Dutch word meaning the yoke of an egg referring to the yellow color of some of the flowers of Cuscuta. Dodder is an annual but some of its connections to the host plant (haustoria) may survive the winter and start new plants already on the host in the spring. The vines always seem to wrap around the host plant in a counterclockwise direction. Dodder is a speed demon when it comes to finding a host. Germination, emergence and attachment to the host may occur in as little as 24 hours and the seedling must find a host in 5-10 days or it will die.

State Ranking Justification

There are five existing populations that have been surveyed since the species was discovered in New York in 1996. Specimens need to be examined in herbaria to discover if the species was in New York before that.

Short-term Trends

There has not been enough recent survey work to determine short-term trends.

Long-term Trends

This species seems to be increasing its presence in New York. It was not known in the state before 1996 and there are now at least five existing occurrences. It may have been present in the state long before 1996 but was not distinguished from more common species.

Conservation and Management

Threats

Southern dodder may prefer purple loosestrife and the control of this invasive species may also reduce populations of this rare plant. Not enough survey work has been done to fully understand the threats to the species.

Conservation Strategies and Management Practices

Management to protect the host plant will serve to protect Southern dodder. This may not be possible if it means protecting purple loosestrife in wetland areas.

Research Needs

The natural history of this species needs to be studied more in New York, especially its habitat and host plant preference, as well as its seed bank production and dispersal. Taxonomic work needs to be done to check specimens of Cuscuta gronovii and its varieties to see if they have been misidentified and are actually this species.

Habitat

Habitat

The few collections of this species in New York have been from swamps and marshes; more information on its habitat requirements is needed. It has been found growing on smartweed (Polygonum hydropoperoides), jewelweed (Impatiens capensis), and purple loosestrife (Lythrum salicaria)(New York Natural Heritage Program 2007).

Associated Species

Range

New York State Distribution

In New York this species has been found at only a few sites from the New York City area and up the Hudson Valley as far as Greene County.

Global Distribution

Cuscuta obtusiflora var. glandulosa reaches its northeastern limit in New York. There are known locations in Connecticut, Minnesota, and California, across the southern states and south to the Caribbean; another variety of the same species occurs in South America.

Best Places to See

Magnolia Swamp (Richmond County)

Identification Comments

General Description

Dodders are parasitic, annual plants, the seedlings attaching to a host plant soon after they sprout. The mature plants lack chlorophyll, roots, or leaves. They consist only of the pale yellow or orangish stems, attached to the host plant via numerous haustoria (suckers), and the compact (2-2.5mm) flowers. With prolific individuals, the overall appearance is of a tangled mass of bumpy orange string sprawled and twining over the host plant. Upon closer inspection, southern dodder has nearly sessile, white, 5-parted flowers which form dense clusters. The sepals are united at the base, and the calyx-lobes reach to the sinuses of the corolla. The fruits are commonly wider than they are high, with a depressed beak (Gleason and Cronquist 1991).

Best Life Stage for Proper Identification

This species is best identified when in flower.

Similar Species

Cuscuta gronovii and C. umbrosa (C. megalocarpa) are the two other species of dodder which occur in New York and have united sepals, 5-parted flowers, and acute corolla lobes. These two species may be distinguished from Cuscuta obtusiflora var. glandulosa by having calyx lobes that do not reach the sinuses of the corolla, and fruit that tend to be higher than thick. Cuscuta gronovii var. latiflora, which occurs on Long Island, has similar flowers to Cuscuta obtusiflora var. glandulosa but the fruit is round or elliptic with a protruding beak, not wider than high with a depressed beak like the fruit of C. obtusiflora var. glandulosa.

Best Time to See

This species flowers from August through September, and the fruits persist through mid-November.

Flowering

Fruiting

The time of year you would expect to find Southern Dodder flowering and fruiting in New York.

Other References

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.

Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.

New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.

New York Natural Heritage Program. 2019. New York Natural Heritage Program Databases. Albany, NY.

Weldy, Troy W. and David Werier. 2005. New York Flora Atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research. University of South Florida]. New York Flora Association, Albany, NY. Available on the web at (http://atlas.nyflora.org/).